Expansion joints for panels in solar boilers

ABSTRACT

A boiler for a solar receiver includes a first receiver panel having a plurality of substantially parallel boiler tubes fluidly connecting an inlet header of the panel to an outlet header of the panel. A second receiver panel has a plurality of substantially parallel boiler tubes fluidly connecting an inlet header of the panel to an outlet header of the panel. The boiler tubes of the second receiver panel are substantially parallel to the boiler tubes of the first receiver panel. The first and second receiver panels are separated by a gap. A panel expansion joint is connected to the first and second receiver panels across the gap, wherein the panel expansion joint is configured and adapted to allow for lengthwise thermal expansion and contraction of the receiver panels along the boiler tubes, and to allow for lateral thermal expansion and contraction of the receiver panels toward and away from one another, while blocking solar radiation through the gap.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/701,999, filed Feb. 8, 2010, claiming priority to U.S. ProvisionalApplication No. 61/151,984, filed Feb. 12, 2009, to U.S. ProvisionalApplication No. 61/152,011, filed Feb. 12, 2009, to U.S. ProvisionalApplication No. 61/152,035, filed Feb. 12, 2009, to U.S. ProvisionalApplication No. 61/152,049, filed Feb. 12, 2009, to U.S. ProvisionalApplication No. 61/152,077, filed Feb. 12, 2009, to U.S. ProvisionalApplication No. 61/152,114, filed Feb. 12, 2009, and to U.S. ProvisionalApplication No. 61/152,286, filed Feb. 13, 2009, each of which isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to solar power production, and moreparticularly, to solar receiver panels for use in solar boilers.

2. Description of Related Art

Solar power generation has been considered a viable source to helpprovide for energy needs in a time of increasing consciousness of theenvironmental aspects of power production. Solar energy productionrelies mainly on the ability to collect and convert energy freelyavailable from the sun and can be produced with very little impact onthe environment. Solar power can be utilized without creatingradioactive waste as in nuclear power production, and without producingpollutant emissions including greenhouse gases as in fossil fuel powerproduction. Solar power production is independent of fluctuating fuelcosts and does not consume non-renewable resources.

Solar power generators generally employ fields of controlled mirrors,called heliostats, to gather and concentrate sunlight on a receiver toprovide a heat source for power production. A solar receiver typicallytakes the form of a panel of tubes conveying a working fluidtherethrough. Previous solar generators have used working fluids such asmolten salt because it has the ability to store energy, allowing powergeneration when there is no solar radiation. The heated working fluidsare typically conveyed to a heat exchanger where they release heat intoa second working fluid such as air, water, or steam. Power is generatedby driving heated air or steam through a turbine that drives anelectrical generator.

More recently, it has been determined that solar power production can beincreased and simplified by using water/steam as the only working fluidin a receiver that is a boiler. This can eliminate the need for aninefficient heat exchanger between two different working fluids. Thisdevelopment has lead to new challenges in handling the intense solarheat without damage to the system. One such challenge involves the factthat traditional boilers are made up of multiple individual boilerpanels sized to facilitate manufacture and maintenance. The intense heatfluxes in solar applications can be around 2-3 times higher than intypical fossil fuel boilers. Additionally, unlike fossil fuel boilers,solar boilers operate on a daily cycle, shutting down in the night. Thehigh heat fluxes and frequency of operation cycles create challengeswith respect to managing thermal expansion and contraction of the boilerpanels. One such challenge is that panels expand vertically along theirlength as well as laterally across their width. If gaps are used betweenpanels to allow for their thermal expansion, care must be exercised toprotect structures and spaces behind the panels from solar radiationpassing through the gaps, which is known as leakage. Also, gaps in thereceiver area of a boiler constitute area where available sunlight fromthe heliostats is not captured.

While previously known systems of solar power production have generallybeen considered satisfactory for their intended purposes, there hasremained a need in the art for solar receivers that can improve theaccommodation of thermal expansion and protect the boiler from leakageof solar radiation. There also has remained a need in the art for suchsolar receivers that are easy to make and use. The present inventionprovides a solution to these problems.

SUMMARY OF THE INVENTION

The subject invention is directed to a new and useful boiler for a solarreceiver. The boiler includes a first receiver panel having a pluralityof substantially parallel boiler tubes fluidly connecting an inletheader of the panel to an outlet header of the panel. A second receiverpanel has a plurality of substantially parallel boiler tubes fluidlyconnecting an inlet header of the panel to an outlet header of thepanel. The boiler tubes of the second receiver panel are substantiallyparallel to the boiler tubes of the first receiver panel. The first andsecond receiver panels are separated by a gap. A panel expansion jointis connected to the first and second receiver panels across the gap,wherein the panel expansion joint is configured and adapted to allow forlengthwise thermal expansion and contraction of the receiver panelsalong the boiler tubes, and to allow for lateral thermal expansion andcontraction of the receiver panels toward and away from one another,while blocking solar radiation through the gap.

In certain embodiments, the first and second receiver panels aresubstantially coplanar. It is also contemplated that the first an secondreceiver panels can be substantially perpendicular. The panel expansionjoint can include a flexible panel expansion shield configured to blocksolar radiation through the gap and to flex to allow for lateral thermalexpansion and contraction of the receiver panels toward and away fromone another. The panel expansion shield can define elongated slots andcan be attached to the first and second receiver panels by fastenerspassing through the elongated slots to accommodate panel thermalexpansion and compression along the slots.

The invention also includes a boiler for a solar receiver that includesT-bar assemblies. The boiler includes a first receiver panel having aplurality of substantially parallel boiler tubes fluidly connecting aninlet header of the panel to an outlet header of the panel. A secondreceiver panel has a plurality of substantially parallel boiler tubesfluidly connecting an inlet header of the panel to an outlet header ofthe panel. The boiler tubes of the second receiver panel aresubstantially parallel to the boiler tubes of the first receiver panel.The first and second receiver panels are separated by a gap. First andsecond T-bar assemblies are each attached to a backside of a respectiveone of said receiver panels. The T-bar assemblies are slidably connectedby a connecting plate fixedly attached to one of the T-bar assemblies,and a fastener inserted through an elongated slot in said connectingplate and fixedly secured to the other one of the T-bar assemblies. Anendmost tube of each of said panels is attached to an adjacent tube ofthe respective panel by a membrane at an angle such that adjacentendmost tubes are displaced from a plane defined by the tubes in each ofthe respective first and second receiver panels in opposite directions,such that solar radiation is prevented from passing through the gap andsuch that lateral thermal expansion and contraction of the receiverpanels toward and away from one another is permitted by the slidableconnector of the T-bar assemblies.

In accordance with certain embodiments, the panels form a corner withrespect to one another, and each of the endmost tubes at the corner isrigidly connected by a membrane at about a 45° angle with respect toeach of the receiver panels. Each of the T-bar assemblies can includeupper and lower tube clips welded to every other boiler tube of eachsaid panel. A first plate can be inserted into the upper and lower tubeclips, the first plate running the width of each panel. A support platecan be inserted behind the first plate into the upper and lower tubeclips, resting on the lower tube clip and running the width of eachpanel and having a space between the support plate and the upper tubeclips to allow for thermal expansion. A T-bar can be welded to thesupport plate for each panel such that it is arranged substantiallyperpendicularly to the support plate. The connecting plate can slidablyconnect adjoining T-bars at the panel gap.

These and other features of the systems and methods of the subjectinvention will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject inventionappertains will readily understand how to make and use the devices andmethods of the subject invention without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 is a side elevation view of a portion of a solar boilerconstructed in accordance with the present invention, showing thereceiver surface and the interior surface of the panel;

FIG. 2 is an interior elevation view of a portion of the solar boiler ofFIG. 1, showing the tubing of the panels as well as the headers;

FIG. 3 is a cross-sectional view of a first exemplary embodiment of anexpansion joint for solar boiler panels constructed in accordance withthe present invention, showing the panel expansion shield spanning thegap between two adjacent boiler panels;

FIG. 4 is an interior elevation view of the expansion joint of FIG. 3,showing the slotted holes for attaching the panel expansion shield tothe panels while accommodating for vertical thermal expansion andcontraction of the panels;

FIG. 5 is a cross-sectional view of a second exemplary embodiment of anexpansion joint for solar boiler panels constructed in accordance withthe present invention, showing how corner panels can be accommodated bya corner panel expansion shield;

FIG. 6 is a cross-sectional view of a third exemplary embodiment of anexpansion joint constructed in accordance with the present invention,showing two plates that can slide over one another to allow for lateralthermal expansion;

FIG. 7 is a interior elevation view of the expansion joint of FIG. 6,showing the alignment of the plates;

FIG. 8 is a cross-sectional view of a fourth exemplary embodiment of anexpansion joint constructed in accordance with the present invention,showing how corner panels can be accommodated by a corner panelexpansion shield;

FIG. 9 is an interior elevation view of the expansion joint of FIG. 8,showing the expansion joint attached to corner panels of a boiler;

FIG. 10 is a partial cross-sectional view of a fifth exemplaryembodiment of an expansion joint constructed in accordance with thepresent invention;

FIGS. 11( a) and 11(b) show how the fifth exemplary embodiment utilizesa T-bar assembly, where FIG. 11( a) is a partial cross-sectional view ofa T-bar assembly and FIG. 11( b) is a top view of a T-bar assembly; and

FIG. 12 is an isolated top cross-sectional view of a corner assembly ofthe fifth exemplary embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectinvention. For purposes of explanation and illustration, and notlimitation, a partial view of a boiler in accordance with the inventionis shown in FIG. 1 and is designated generally by reference character100. Exemplary embodiments of a boiler in accordance with the invention,or aspects thereof, are provided in FIGS. 2-12, as will be described.The systems of the invention can be used to more effectively accommodatevertical and lateral thermal expansion in boiler panels while limitingleakage of solar radiation, for example in solar power generation.

A typical boiler is split into panels, which are sized to facilitatemanufacturing, shipping, and assembly. Due to the unique heat flux insolar applications, specifically the large variations in heat fluxexperienced over small areas, each panel must be allowed to thermallyexpand and grow independently from the adjacent panels. Typically, thereis a gap to allow for such thermal expansion, however, leaving a gapbetween panels allows concentrated solar radiation to penetrate into theboiler, i.e. leakage, exposing equipment inside. To prevent this, thesystem in accordance with the present invention is configured to reduceor eliminate radiation leakage, while still allowing for thermalexpansion, both vertically and horizontally. The system consists of apanel expansion shield constructed of steel or any suitable material,which is fastened through slotted holes therethrough to the adjacenttubes across a gap between panels. The slotted hole allows for varyingvertical expansion between panels. The shield itself is designed to flexinward as the panels grow toward each other. A panel expansion shieldcan also be configured to prevent radiation leakage at corner panels,where two panels meet perpendicular to each other. By using a panelexpansion shield corner panels are allowed to grow in two dimensions,while maintaining a barrier to concentrated solar radiation.

With reference now to FIG. 1, boiler 100 for a solar receiver includes afirst boiler panel 102, of a steam generator section for example, havinga plurality of tubes fluidly connecting an inlet header of the firstboiler (not shown, but see, e.g., 112) panel 102 to an outlet header 104of the first boiler panel 102. The tubes of first boiler panel 102 forma first solar receiver surface 106 and a first internal surface 108opposite first solar receiver surface 106. The exterior receiver surface106 receives solar energy, for example from a field of heliostats, asindicated by arrows in FIG. 1.

A second boiler panel 110, of a superheater section, for example,similarly includes a plurality of tubes fluidly connecting an inletheader 112 of second boiler panel 110 to an outlet header 114 of secondboiler panel 110. The tubes of second boiler panel 110 forming a secondsolar receiver surface 116 and a second internal surface 118 oppositethe second solar receiver surface (i.e. external and internal surfaces,respectively, as indicated in FIG. 1). Like receiver surface 106,exterior receiver surface 116 receives solar energy, for example, from afield of heliostats, as indicated by arrows in FIG. 1.

First and second boiler panels 102 and 110 are adjacent one another withan end 120 of first solar receiver surface 106 overlapping an end 122 ofsecond boiler panel 110 to reduce solar radiation passing between thefirst and second solar receiver surfaces 106 and 116. The interiorsurfaces have a layer of insulating material 124 to protect the interiorspace and components from the high external temperatures. FIG. 2 showsthe same portion of boiler 100 from the interior, with insulatingmaterial 124 removed to show the tubes and headers.

Referring now to a first exemplary embodiment as shown in FIG. 3, boiler100 includes a first receiver panel 110 a having a plurality ofsubstantially parallel boiler tubes 210 fluidly connecting an inletheader of the panel 110 a to an outlet header of the panel, as describedabove. A second receiver panel 110 b has a plurality of substantiallyparallel boiler tubes 210 fluidly connecting an inlet header of thepanel to an outlet header of the panel 110 b, as described above. Theboiler tubes 210 of second receiver panel 110 b are substantiallyparallel to the boiler tubes 210 of first receiver panel 110 a. Thefirst and second receiver panels 110 a,b are separated by a gap 11. Apanel expansion shield 10 is connected to the first and second receiverpanels 110 a,b across gap 11.

Panel expansion shield includes a bend 12 which can flex to allow forlateral (width-wise) thermal expansion and contraction of the receiverpanels toward and away from one another, as indicated by arrows in FIG.3. Panel expansion shield 10 runs vertically along substantially theentire length of panels 110 a,b to block solar radiation through gap 11.

Panel expansion shield 10 is also configured and adapted to allow forvertical thermal expansion and contraction of the receiver panels alongthe lengthwise direction boiler tubes 210, as indicated by arrows inFIG. 4. As shown in FIG. 4, panel expansion shield 10 has elongatedslots 16 and is attached to first and second receiver panels 110 a,b byfasteners 14 passing through elongated slots 16 to accommodate verticalthermal expansion of panels 110 a,b and to allow for differences inthermal expansion.

In FIGS. 3-4, first and second receiver panels 110 a,b are substantiallycoplanar with each other. As indicated in FIG. 5, in a second exemplaryembodiment, it is also contemplated that first and second receiverpanels 110 a,b can be substantially perpendicular to one another, as ata corner of a solar boiler, for example. Panel expansion shield 20 isconfigured to prevent radiation leakage at the corners of the boiler.Panel expansion shield 20 consists of a single bent steel plate. Thoseskilled in the art will readily appreciate that any suitable materialcan be used without departing from the spirit and scope of theinvention. Panel expansion shield 20 accommodates vertical movement ofpanels 110 a,b in the same manner as panel expansion shield 10, that is,by vertical slot attachments for fasteners 14. While shown and describedas accommodating a right angle, those skilled in the art will readilyappreciate that panel expansion shields can be configured to accommodateany suitable angle without departing from the spirit and scope of theinvention.

In order to withstand the high heat flux and shield internal componentsagainst leakage of solar radiation, panel expansion shields 10 and 20are made of steel, ceramics, or any other suitable material. Rods 215are used to attach tubes 210 together, as indicated in FIG. 3. Thisprevents leakage between tubes, provides support for the tubes, andallows for the tubes to flex as in thermal expansion and contraction.Rods 215 allow tubes 210 to be closer together (i.e., tangent),increasing the effective solar receiver area compared to panels withmembranes between the tubes.

FIGS. 6-7 show a cross-sectional and interior elevation view,respectively, of another exemplary expansion shield 30 in accordance athird exemplary embodiment of the present invention. Expansion shield 30includes a first plate 32 a fastened to one panel and a second plate 32b fastened to an adjacent panel. Plate 32 a includes an overlap plate33. Plates 32 a and 32 b slide over one another to allow for lateral andvertical thermal expansion.

FIGS. 8-9 show cross-sectional and interior elevation views,respectively, of a fourth exemplary embodiment showing a cornerexpansion shield 40 in accordance with the invention. Corner expansionshield 40 operates much the same as corner expansion shield 20 describedabove, with a different cross-sectional shape that keeps the bend of theshield more to the interior of the boiler. Those skilled in the art willreadily appreciate that any suitable cross-sectional shape can be usedwithout departing from the spirit and scope of the invention.

FIGS. 10, 11(a) and 11(b) show a fifth exemplary embodiment of thepresent invention. Panels 110 a and 110 b are arranged in-line andparallel to one another with a gap 550 between the panels. Lower tubeclips 514 are welded to boiler tubes 210, as shown in FIG. 11( a). Astainless steel plate 506 is inserted into lower tube clips 514, restingon its lower edge. Each panel 110 a and 110 b has an individualstainless steel plate 506 which runs the width of each panel, i.e.,substantially perpendicular to the tubes. A back steel support plate 510is inserted behind stainless steel plate 506 into lower tube clips 514.Similar to the stainless steel plate 506, back support steel plate 510rests on the lower tube clips 514 and runs the width of each panel 110 aand 110 b. Upper tube clips 515 are then welded to tubes 210, holdingstainless steel plate 506 and back support steel plate 510 in place.Stainless steel plate 506 serves to protect the support assembly 540from penetrating solar radiation. T-bar 518 is then welded perpendicularto back steel support 510 to create a rigid strong back. Assembly 540serves to hold each boiler tube 210 from bowing outward. Connectingplate 522 connects adjoining T-bars 518. Bolt 526 secures connectingplate 522 to adjoining T-bars 518. Connecting slot 530 allows bolt 526to move horizontally, which allows panels 110 a and 110 b to expandtowards each other freely. At panel gap 550 two boiler tubes 210 areheld out-of-plane by membrane 502. The out-of-plane tubes 210 serve toprotect the panel gap 550 from penetrating solar radiation. As theboiler 100 heats up during operation, panels 110 a and 110 b growtogether to close gap 550.

While the gaps in-between the panels 110 a, 110 b are sealed with out ofplane tubes 210 to allow for expansion, the corners are rigidlyconnected together, as shown in FIG. 12, because the corner panelsexpand away from the corner, as indicated by arrows in FIG. 12. This isbecause all of the thermal expansion is away from the corners of theboiler 100. To create the seal in the corners the last tubes 210 of theperpendicular corner panels 110 a, 110 b switch from tangent to membraneconnectors. A single piece of membrane 502 is then welded at a 45 degreeangle with respect to the panels 110 a, 110 b, to each of the two tubes210 that form the corner of the boiler 100. This creates a solid andsealed corner formed of tubes 210 and membrane 502 which does not allowany radiation to penetrate the boiler.

The methods and systems of the present invention, as described above andshown in the drawings provide for expansion joints between panels insolar boilers. This configuration provides improved accommodation ofthermal expansion in the vertical and lateral directions of the panelswhile also providing protection of components and spaces internal to thereceiver panels from leakage of solar radiation from the heliostats.

While the apparatus and methods of the subject invention have been shownand described with reference to preferred embodiments, those skilled inthe art will readily appreciate that changes and/or modifications may bemade thereto without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A boiler for a solar receiver comprising: a) afirst receiver panel having a plurality of substantially parallel boilertubes fluidly connecting an inlet header of the panel to an outletheader of the panel; b) a second receiver panel having a plurality ofsubstantially parallel boiler tubes fluidly connecting an inlet headerof the panel to an outlet header of the panel, wherein the boiler tubesof the second receiver panel are substantially parallel to the boilertubes of the first receiver panel, and wherein the first and secondreceiver panels are separated by a gap; c) a panel expansion jointconnected to the first and second receiver panels across the gap,wherein the panel expansion joint is configured and adapted to allow forlengthwise thermal expansion and contraction of the receiver panelsalong the boiler tubes, and to allow for lateral thermal expansion andcontraction of the receiver panels toward and away from one another,while blocking solar radiation through the gap, wherein the panelexpansion joint includes first and second T-bar assemblies each attachedto a backside of a respective one of said receiver panels, the T-barassemblies being slidably connected by a connecting plate fixedlyattached to one of the T-bar assemblies, and a fastener inserted throughan elongated slot in said connecting plate and fixedly secured to theother one of the T-bar assemblies.
 2. A boiler for a solar receivercomprising: a) a first receiver panel having a plurality ofsubstantially parallel boiler tubes fluidly connecting an inlet headerof the panel to an outlet header of the panel; b) a second receiverpanel having a plurality of substantially parallel boiler tubes fluidlyconnecting an inlet header of the panel to an outlet header of thepanel, wherein the boiler tubes of the second receiver panel aresubstantially parallel to the boiler tubes of the first receiver panel,the first and second receiver panels being separated by a gap; and c)first and second T-bar assemblies each attached to a backside of arespective one of said receiver panels, the T-bar assemblies beingslidably connected by a connecting plate fixedly attached to one of theT-bar assemblies, and a fastener inserted through an elongated slot insaid connecting plate and fixedly secured to the other one of the T-barassemblies, wherein an endmost tube of each of said panels is attachedto an adjacent tube of the respective panel by a membrane at an anglesuch that adjacent endmost tubes are displaced from a plane defined bythe tubes in each of the respective first and second receiver panels inopposite directions, such that solar radiation is prevented from passingthrough the gap and such that lateral thermal expansion and contractionof the receiver panels toward and away from one another is permitted bythe slidable connector of the T-bar assemblies.
 3. A boiler as recitedin claim 2, wherein the panels form a corner with respect to oneanother, and wherein each of the endmost tubes at the corner is rigidlyconnected by a membrane at about a 45° angle with respect to each of thereceiver panels.
 4. A boiler as recited in claim 2, wherein each of theT-bar assemblies comprises: upper and lower tube clips welded to everyother boiler tube of each said panel; a first plate inserted into theupper and lower tube clips, the first plate running the width of eachpanel; a support plate inserted behind the first plate into the upperand lower tube clips, resting on the lower tube clip and running thewidth of each panel and having a space between the support plate and theupper tube clips to allow for thermal expansion; and a T-bar welded tothe support plate for each panel such that it is arranged substantiallyperpendicularly to the support plate, wherein the connecting plateslidably connects adjoining T-bars at the panel gap.